I've been looking around for a reference to defending. I see it mentioned on a couple of cards, and once in the rule book:
A player may spend (discard) a Support Token from one of his Space Marines when it is attaching or defending to reroll a die that was just rolled.
What is the defending? Does it mean when you are attacking the Space Marine with the genestealer? I would like some clarification if anyone can offer it. Thanks.